Zenmap Alternatives for Linux

Nmap is a free and open-source utility for network discovery and security auditing. It utilizes raw IP packets to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. It is command-line driven, though official GUI versions are also available.

Angry IP Scanner is a free, open-source network scanner designed for speed and simplicity. It quickly scans IP addresses and ports across any range, making it an essential tool for network administrators and users needing to discover devices on their network.

Skipfish is a discontinued command-line web application security scanner known for its recursive crawling and heuristic detection capabilities. It's designed to quickly assess web applications for common vulnerabilities and security flaws.